For every person using 4G LTE now, there will be at least one more subscriber by the end of this year, IHS iSuppli says.

The number of users on LTE services will slightly more than double in 2013, growing by 115 percent to 198.1 million people worldwide, according to the research company. At the end of 2012, there were 92.3 million subscribers, iSuppli said.

Many consumers are getting into LTE as they update their smartphones and the areas served by LTE also continue to grow, according to an IHS iSuppli press release. Most early LTE adoption took place in Europe and Asia, but North America drove major growth in 2011 and 2012, the company said. In the U.S., Verizon Wireless, AT&T and Sprint Nextel continue to expand their LTE footprints, while T-Mobile and Sprint partner Clearwire plan to start deploying the technology this year.

The pace of LTE adoption will actually slow this year, because the number of new users grew 599 percent in 2012, iSuppli said. But that increase came on top of a much smaller base of just 13.2 million subscribers at the beginning of that year. LTE was first offered in 2010.

LTE provides both higher speeds and shorter delays than earlier 3G technology, which is still much more widely used than LTE. That's helping to open the door to emerging uses of mobile data such as video and gaming, though most voice calls are still carried over older circuit-switched 2G and 3G systems. Over the next few years, carriers are expected to start sending voice calls over LTE as another form of data.

As LTE becomes mainstream, international roaming with the technology may lag behind. There are more than 40 different frequency bands defined for LTE, so makers of smartphones, tablets and other devices face a complex set of choices about which to include in their products, according to IHS iSuppli. This fragmentation is worse than vendors faced with 3G, and it has had repercussions. Apple drew criticism and even legal action for launching the iPad 3 without a radio for Band 3, a band around 1800MHz that is widely used for LTE.

With different regulations in various parts of the world, it's still unclear whether consumers will be able to use their LTE devices on the fast network technology outside their home countries. Carrier policies will also play a role in whether roaming service is available.

By 2016, roaming is likely to become a more widespread need. IHS iSuppli estimates there will be 1 billion LTE subscribers worldwide by that time.